// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "sandbox/win/src/wow64.h"

#include <sstream>

#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/win/scoped_process_information.h"
#include "base/win/windows_version.h"
#include "sandbox/win/src/target_process.h"

namespace {

// Holds the information needed for the interception of NtMapViewOfSection on
// 64 bits.
// Warning: do not modify this definition without changing also the code on the
// 64 bit helper process.
struct PatchInfo32 {
  HANDLE dll_load;  // Event to signal the broker.
  ULONG pad1;
  HANDLE continue_load;  // Event to wait for the broker.
  ULONG pad2;
  HANDLE section;  // First argument of the call.
  ULONG pad3;
  void* orig_MapViewOfSection;
  ULONG original_high;
  void* signal_and_wait;
  ULONG pad4;
  void* patch_location;
  ULONG patch_high;
};

// Size of the 64 bit service entry.
const SIZE_T kServiceEntry64Size = 0x10;

// Removes the interception of ntdll64.
bool Restore64Code(HANDLE child, PatchInfo32* patch_info) {
  PatchInfo32 local_patch_info;
  SIZE_T actual;
  if (!::ReadProcessMemory(child, patch_info, &local_patch_info,
                           sizeof(local_patch_info), &actual))
    return false;
  if (sizeof(local_patch_info) != actual)
    return false;

  if (local_patch_info.original_high)
    return false;
  if (local_patch_info.patch_high)
    return false;

  char buffer[kServiceEntry64Size];

  if (!::ReadProcessMemory(child, local_patch_info.orig_MapViewOfSection,
                           &buffer, kServiceEntry64Size, &actual))
    return false;
  if (kServiceEntry64Size != actual)
    return false;

  if (!::WriteProcessMemory(child, local_patch_info.patch_location, &buffer,
                            kServiceEntry64Size, &actual))
    return false;
  if (kServiceEntry64Size != actual)
    return false;
  return true;
}

typedef BOOL (WINAPI* IsWow64ProcessFunction)(HANDLE process, BOOL* wow64);

}  // namespace

namespace sandbox {

Wow64::Wow64(TargetProcess* child, HMODULE ntdll)
    : child_(child), ntdll_(ntdll), dll_load_(NULL), continue_load_(NULL) {
}

Wow64::~Wow64() {
}

// The basic idea is to allocate one page of memory on the child, and initialize
// the first part of it with our version of PatchInfo32. Then launch the helper
// process passing it that address on the child. The helper process will patch
// the 64 bit version of NtMapViewOfFile, and the interception will signal the
// first event on the buffer. We'll be waiting on that event and after the 32
// bit version of ntdll is loaded, we'll remove the interception and return to
// our caller.
bool Wow64::WaitForNtdll() {
  if (base::win::OSInfo::GetInstance()->wow64_status() !=
      base::win::OSInfo::WOW64_ENABLED)
    return true;

  const size_t page_size = 4096;

  // Create some default manual reset un-named events, not signaled.
  dll_load_.Set(::CreateEvent(NULL, TRUE, FALSE, NULL));
  continue_load_.Set(::CreateEvent(NULL, TRUE, FALSE, NULL));
  HANDLE current_process = ::GetCurrentProcess();
  HANDLE remote_load, remote_continue;
  DWORD access = EVENT_MODIFY_STATE | SYNCHRONIZE;
  if (!::DuplicateHandle(current_process, dll_load_.Get(), child_->Process(),
                         &remote_load, access, FALSE, 0)) {
    return false;
  }
  if (!::DuplicateHandle(current_process, continue_load_.Get(),
                         child_->Process(), &remote_continue, access, FALSE,
                         0)) {
    return false;
  }

  void* buffer = ::VirtualAllocEx(child_->Process(), NULL, page_size,
                                  MEM_COMMIT, PAGE_EXECUTE_READWRITE);
  DCHECK(buffer);
  if (!buffer)
    return false;

  PatchInfo32* patch_info = reinterpret_cast<PatchInfo32*>(buffer);
  PatchInfo32 local_patch_info = {0};
  local_patch_info.dll_load = remote_load;
  local_patch_info.continue_load = remote_continue;
  SIZE_T written;
  if (!::WriteProcessMemory(child_->Process(), patch_info, &local_patch_info,
                            offsetof(PatchInfo32, section), &written))
    return false;
  if (offsetof(PatchInfo32, section) != written)
    return false;

  if (!RunWowHelper(buffer))
    return false;

  // The child is intercepted on 64 bit, go on and wait for our event.
  if (!DllMapped())
    return false;

  // The 32 bit version is available, cleanup the child.
  return Restore64Code(child_->Process(), patch_info);
}

bool Wow64::RunWowHelper(void* buffer) {
  static_assert(sizeof(buffer) <= sizeof(DWORD), "unsupported 64 bits");

  // Get the path to the helper (beside the exe).
  wchar_t prog_name[MAX_PATH];
  GetModuleFileNameW(NULL, prog_name, MAX_PATH);
  base::string16 path(prog_name);
  size_t name_pos = path.find_last_of(L"\\");
  if (base::string16::npos == name_pos)
    return false;
  path.resize(name_pos + 1);

  std::basic_stringstream<base::char16> command;
  command << std::hex << std::showbase << L"\"" << path <<
               L"wow_helper.exe\" " << child_->ProcessId() << " " <<
               bit_cast<ULONG>(buffer);

  scoped_ptr<wchar_t, base::FreeDeleter>
      writable_command(_wcsdup(command.str().c_str()));

  STARTUPINFO startup_info = {0};
  startup_info.cb = sizeof(startup_info);
  PROCESS_INFORMATION temp_process_info = {};
  if (!::CreateProcess(NULL, writable_command.get(), NULL, NULL, FALSE, 0, NULL,
                       NULL, &startup_info, &temp_process_info))
    return false;
  base::win::ScopedProcessInformation process_info(temp_process_info);

  DWORD reason = ::WaitForSingleObject(process_info.process_handle(), INFINITE);

  DWORD code;
  bool ok =
      ::GetExitCodeProcess(process_info.process_handle(), &code) ? true : false;

  if (WAIT_TIMEOUT == reason)
    return false;

  return ok && (0 == code);
}

// First we must wake up the child, then wait for dll loads on the child until
// the one we care is loaded; at that point we must suspend the child again.
bool Wow64::DllMapped() {
  if (1 != ::ResumeThread(child_->MainThread())) {
    NOTREACHED();
    return false;
  }

  for (;;) {
    DWORD reason = ::WaitForSingleObject(dll_load_.Get(), INFINITE);
    if (WAIT_TIMEOUT == reason || WAIT_ABANDONED == reason)
      return false;

    if (!::ResetEvent(dll_load_.Get()))
      return false;

    bool found = NtdllPresent();
    if (found) {
      if (::SuspendThread(child_->MainThread()))
        return false;
    }

    if (!::SetEvent(continue_load_.Get()))
      return false;

    if (found)
      return true;
  }
}

bool Wow64::NtdllPresent() {
  const size_t kBufferSize = 512;
  char buffer[kBufferSize];
  SIZE_T read;
  if (!::ReadProcessMemory(child_->Process(), ntdll_, &buffer, kBufferSize,
                           &read))
    return false;
  if (kBufferSize != read)
    return false;
  return true;
}

}  // namespace sandbox